<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>mask</title>
  <style>
    * {
      margin: 0;
      padding: 0;
      user-select: none;
      -webkit-user-drag: none;
    }
    body {
      width: 100%;
      height: 100%;
      background-color: rgba(255, 255, 255, 0);
      transition: background-color 120ms linear;
    }
  </style>
</head>
<body draggable="false"></body>
</html>
